(function (exports) {
    var streams = [];
    var free_ids = [];
    var next_id = 0;

    function URLStream(ud, idx) {
        console.log("new URLStream created with idx=" + idx + " and ud=" + ud);
        this.idx = idx;
        this.ud = ud;
        this.request = new XMLHttpRequest();
        this.url = null;
        this.request.responseType = 'arraybuffer';
        this.method = "GET";
        this.data = null;
        this.buffer_ptr = 0;
        this.buffer_len = 0;
    }

    exports._urlstream_set_buffer = function (idx, ptr, len) {
        var stream = streams[idx];
        if (!stream) {
            throw new Error("invalid stream index");
        }
        stream.buffer_ptr = ptr;
        stream.buffer_len = len;
    };

    exports._urlstream_set_url = function (idx, url) {
        var stream = streams[idx];
        if (!stream) {
            throw new Error("invalid stream index");
        }
        stream.url = UTF8ToString(url);
    };

    exports._urlstream_set_data = function (idx, ptr, len) {
        var stream = streams[idx];
        if (!stream) {
            throw new Error("invalid stream index");
        }
        stream.data = new Blob([new Uint8Array(HEAPU8.subarray(ptr, ptr + len))]);
    };

    exports._urlstream_destroy = function (idx) {
        var stream = streams[idx];
        if (!stream) {
            throw new Error("invalid stream index");
        }
        stream.ud = 0;
        streams[idx] = null;
        free_ids.push(idx);
    };

    exports._urlstream_load = function (idx) {
        var stream = streams[idx];
        if (!stream) {
            throw new Error("invalid stream index");
        }

        function report_fail(code, message) {
            if (stream.ud) {
                var ptr = allocate(intArrayFromString(message), 'i8', ALLOC_STACK);
                _urlstream_on_error(stream.idx, stream.ud, code, ptr);
            }
        }

        function on_loadstart(event) {
            if (stream.ud) {
                _urlstream_on_open(stream.idx, stream.ud);
            }
        }

        function on_complete(event) {
            if (stream.ud) {
                var response = stream.request.response;
                if (response) {
                    var byteArray = new Uint8Array(response);
                    var size = byteArray.length;
                    var buffer_ptr = stream.buffer_ptr;
                    var buffer_len = stream.buffer_len;

                    for (var offset = 0; offset < size; offset += buffer_len) {
                        var to_transfer = Math.min(size - offset, buffer_len);
                        HEAPU8.subarray(buffer_ptr, buffer_ptr + to_transfer).set(byteArray.subarray(offset, offset + to_transfer));
                        _urlstream_on_data(stream.idx, stream.ud, buffer_ptr, to_transfer);
                    }
                }
                _urlstream_on_complete(stream.idx, stream.ud);
            }
        }

        function on_error(event) {
            if (event.error) {
                report_fail(event.error.code, event.error.name + ": " + event.error.message);
            } else {
                report_fail(1000, "stream error");
            }
        }

        function on_abort(event) {
            report_fail(300, "aborted");
        }

        function on_progress(event) {
            if (stream.ud) {
                if (event.lengthComputable) {
                    _urlstream_on_progress(stream.idx, stream.ud, event.loaded, event.total);
                } else if ( 'loaded' in event ) {
                    _urlstream_on_progress(stream.idx, stream.ud, event.loaded, 0);
                }
            }
        }

        stream.request.addEventListener("loadstart", on_loadstart);
        stream.request.addEventListener("progress", on_progress);
        stream.request.addEventListener("error", on_error);
        stream.request.addEventListener("abort", on_abort);
        stream.request.addEventListener("load", on_complete);

        stream.request.open(stream.method, stream.url);
        stream.request.send(stream.data);
    };

    exports._urlstream_set_method = function (idx, method) {
        var stream = streams[idx];
        if (!stream) {
            throw new Error("invalid stream index");
        }
        switch (method) {
        case 1: {
            stream.method = "GET";
        } break;
        case 2: {
            stream.method = "POST";
        } break;
        default: {
            throw new Error("invalid URLStream method id");
        } break;
        }
    };

    exports._urlstream_create = function (ud) {
        var idx = 0;
        if (free_ids.length === 0) {
            idx = next_id;
            next_id++;
        } else {
            idx = free_ids.pop();
        }
        var stream = new URLStream(ud, idx);
        streams[idx] = stream;
        return idx;
    };
})(this);